WASHINGTON (Reuters) - Scientific advisers to President Barack Obama may have asked the government to speed up the availability of swine flu vaccines, but they are unlikely to be ready before October, the new head of the U.S. Centers for Disease Control and Prevention said on Wednesday.

And imperfect tests for the pandemic H1N1 virus means it will be impossible to get precise numbers on how many people are infected, said Dr. Thomas Frieden.

Nonetheless, swine flu is the No. 1 priority for the CDC, Frieden said in an interview.

"We have literally mobilized more than 1,000 people at CDC who work on H1N1," Frieden said in the interview, conducted by Reuters and Associated Press to be aired on the C-SPAN television network on Sunday.

On Monday, the President's Council of Advisors on Science and Technology said the government should speed up the supply of swine flu drugs and vaccines, making at least some shots available by mid-September.

The group also said the government should take advantage of the pandemic to improve flu surveillance.

Frieden said it was unlikely vaccines against H1N1 could get out to the public sooner than mid-October, when mass vaccination is scheduled to start.

"We wish we had new vaccine technology that would allow us to turn on a dime and make new vaccine in terms of weeks or months. It's not possible with today's technology to do that," he said.

Five companies are making swine flu vaccine for the U.S. market -- AstraZeneca's MedImmune unit, CSL Ltd, GlaxoSmithKline Plc, Novartis AG and Sanofi-Aventis SA. Tests have begun to determine if people will need one or two doses to be protected.

WORST CASE PREDICTIONS

Frieden also distanced himself from some of the worst-case predictions outlined in the council's report, which included a "plausible" estimate that between 30,000 and 90,000 people might die and up to 1.8 million might clog hospitals.

"Unfortunately, the media coverage of it was not nearly as balanced as the report itself," Frieden said.

"Everything we have seen in the U.S. and everything we have seen around the world to date suggests that we won't see that kind of number if the virus doesn't change."

Because this virus is new, more people are susceptible to it and the World Health Organization has been predicting for months now that 2 billion people will likely become infected.

"We will do everything in our power to reduce the number of people who die," Frieden said.

But officials fear H1N1 could worsen as U.S. schools start their fall terms. Frieden fears there could be a rush of demand for vaccine if that happens.

"As people become sick or severely ill or die from flu we'll get an increased demand for the flu vaccine and that is one of the challenges we have," he said.

The Health and Human Services department estimates only 45 million doses will be available by mid-October, with 20 million a week coming after that.

Asked about surveillance, Frieden said that will be difficult, too. The new flu does not always show up on standard, on-the-spot flu tests given in doctor's offices.

Special tests to differentiate pandemic H1N1 from seasonal flu have been sent to every state health department but it will be impossible to test everyone with symptoms, the tests are not 100 percent reliable, and there is not much point in testing everyone anyway, Frieden said.

"Once flu is in the community most people with flu don't need to be treated," he said. People at high risk of death or severe symptoms, such as pregnant women or people with asthma, need to be treated right away anyhow and it is not worth waiting to test them, he added.